Copper (i) complexes for optoelectronic devices

Abstract

The invention relates to neutral mononuclear copper (I) complexes for emitting light and with a structure according to formula (A) in which: M represents: Cu(I); L∩L represents: a single, negatively charged, bidentate ligand; N∩N represents: a diimine ligand (substituted with R and FG), in particular a substituted 2,2′-bipyridine derivative (bpy) or a substituted 1,10-phenanthroline derivative (phen); R represents: at least one sterically demanding substituent for preventing the planarisation of the complex in the excited state; FG=functional group, and represents: at least one second substituent for increasing solubility in organic solvents. The substituent can also be used for electron transport or alternatively for hole transport, said functional group being bound to the diimine ligands either directly or by means of suitable bridges; and the copper (I) complex: having a ΔE(S1−T1) value of less than 2500 cm−1 between the lowest excited singlet state (S1) and the triplet state (T1) which lies below; having an emission lifespan of at most 20 μs; having an emission quantum yield of greater than 40%, and a solubility of at least 1 g / L in organic solvents, in particular polar organic hydrocarbons such as acetone, methyl ethyl ketone, benzene, toluene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, dichloroethane, tetrachloroethylene, alcohols, acetonitrile or water.

Description

[0001]The present invention relates to the use of soluble copper(I) complexes (Cu(I)-complexes) as emitters in OLEDs (organic light-emitting diodes) and in other optoelectronic devices.INTRODUCTION[0002]A dramatic change is currently on the horizon in the field of visual display and illumination technology. It will be possible to manufacture flat displays or illuminated surfaces having a thickness of less than 0.5 mm. These are notable for many fascinating properties. For example, it will be possible to achieve illuminated surfaces in the form of wallpaper with very low energy consumption. It is also of particular interest that color visual display units will be producible with hitherto unachievable colorfastness, brightness and viewing angle independence, with low weight and with very low power consumption. It will be possible to configure the visual display units as micro-displays or large visual display units of several square meters in area in rigid form or flexibly, or else as ...

AI Technical Summary

Benefits of technology

The patent text discusses the importance of loosening a restriction on the transition between certain states in molecules to create emitter molecules with shorter emission decay times and high quantum yields. The use of these molecules in OLED displays results in better efficiency and longer operating life of the device. The text also describes the use of certain substituents on the molecule to prevent quenching of luminescence and to prevent unwanted reactions with the molecule. Additionally, the text mentions that the attachment of hole conductors to the molecule can be achieved through palladium-catalyzed coupling reactions.

Problems solved by technology

This predominantly involves very expensive noble metals such as iridium, platinum or else gold.

Moreover, a large number of OLED emitter materials known to date are ecologically problematic, so that the use of less toxic materials is desirable, such as copper(I) complexes.

Consequently, further charge carrier streams can no longer lead completely to the occupation of the excited and emitting states.

The result is then unwanted ohmic losses.

This leads to a distinct decline in efficiency of the OLED device with rising current density (called “roll-off” behavior).

For instance, disadvantages are found particularly in the case of use of emitters with long emission lifetimes for OLED illuminations where a high luminance, for example of more than 1000 cd / m2, is required (cf.

Furthermore, molecules in electronically excited states are frequently more chemically reactive than in ground states so that the likelihood of unwanted chemical reactions increases with the length of the emission lifetime.

The occurrence of such unwanted chemical reactions has a negative effect on the lifetime of the device.

Furthermore, Cu(I)-complexes undergo strong geometry changes after the excitation (through electron-hole recombination or through optical excitation) which leads to the reduction of emission quantum yields.

Also, the emission colors are shifted due to these processed towards red, which is unwanted.

Moreover, many of the known copper-complexes are not soluble in the solvents that are needed for technical use.

This is another aspect why the use of such complexes is disfavored.

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